Total electron content (TEC) data measured from ground-based GPS receivers is compared to HF backscatter from ionospheric irregularities obtained by Super Dual Auroral Radar Network (SuperDARN) radars.  We present the first observations of a recurrent region of anomalous enhanced TEC at mid-latitudes over North America and attempt to characterize its frequency of occurrence.  Next, we examine the relationship of convection electric fields to the formation of a polar cap tongue of ionization (TOI) from mid-latitude plumes of storm enhanced density (SED) during a geomagnetic storm on 26 September 2011.  A channel of high density F region plasma was transported from the dayside ionosphere and into the polar cap by enhanced convection electric fields extending to mid-latitudes.  After the solar wind IMF conditions quieted and the dayside convection electric fields retreated to higher latitudes, an SED was observed extending to, but not entering, the dayside cusp region.  The source mechanism (enhanced electric fields) previously drawing the plasma from mid-latitudes and into the polar cap was no longer active, resulting in a fossil feature which persisted for several hours as it elongated in magnetic local time. Finally, we discuss ground surface effects on the HF backscatter observed by four SuperDARN radars. Monthly ground scatter occurrence rates are calculated for comparison with Arctic sea ice boundaries derived from satellite observations, showing reduced backscatter from regions covered by ice. / Master of Science

First time ionospheric refractive index values have been determined at mid latitudes using frequency switched SuperDARN plasma convection velocity estimates. Previous works have found a disparity between high latitude SuperDARN plasma convection velocities and those made by other devices. It was noted that the scattering volume’s refractive index was being neglected when estimating plasma convection velocities, meaning a correction factor was needed in order to more accurately reflect other measurements. Later work proposed a solution which implemented frequency switching in SuperDARN radars and determined a single correction factor based off of many years of data. We present case study driven research which applies the principles of these previous works to mid latitudes in an attempt to determine the refractive effect in mid latitude SuperDARN plasma convection velocity data by examining frequency switched quiet time ionospheric scatter. It was found that the 1/2 hop ionospheric scatter exhibited little to no measurable refractive effect (n ∼ 1), while the 11/2 hop ionospheric scatter tended to exhibit measurable refractive effects (n ∼ 0.7). This is then expanded to a storm-time 1/2 hop ionospheric scatter case study. It was again found that the refractive effects were nearly negligible (n ∼ 1), indicating that the 1/2 hop plasma convection velocities reported by mid latitude SuperDARN radars only require a very small correction factor, if any at all. / Master of Science

The Sub-Auroral Polarization Stream (SAPS) is a narrow, intense and persistent westward (sunward) ionospheric convection flow channel observed equatorward of the auroral electron precipitation boundary, predominantly on the nightside. Previous studies have identified disturbed-time SAPS to be a geomagnetic activity dependent phenomenon, which exhibits average pre-midnight and post-midnight velocities of 1000 m/s and 400 m/s respectively. Numerous studies have reported even narrower and more intense westward plasma flows called SAIDs to be embedded within SAPS channels, especially during substorm recovery phases. Quiet-time SAPS studies, although relatively few, have shown these SAPS to be associated with much weaker velocities and to be influenced by substorm intensifications. However, these studies have been limited in their ability to make simultaneous measurements of SAPS flow velocities over many hours of MLT. The recent expansion of SuperDARN radars to middle latitudes facilitates unprecedented large-scale observations of SAPS over 10 hours of MLT with high temporal and spatial resolution. In this thesis, we first examine the spatial and temporal dynamics of one quiet-time SAPS event, using the mid-latitude SuperDARN radars. The SAPS was identified as elevated flows lying equatorward of the auroral electron precipitation boundary specified by the NOAA POES satellites. We demonstrate the L-shell fitting technique to analyze the dynamics in the strength and direction of the two-dimensional SAPS flow velocities at three separate magnetic longitudes. The quiet-time SAPS event thus examined lasted for over 4 hours in UT and extended over 10 hours of MLT, as is commonly observed for disturbed-time SAPS. However, the decrease in SAPS peak latitudes and peak velocities with MLT and MLon respectively, observed for disturbed-time SAPS, was not observed for this event. We also find the dynamics of the enhancements in the quiet-time SAPS peak velocities, to correlate well with that of substorm intensifications identified using the CARISMA magnetometers. We then identify numerous such conjunctions between quiet-time SAPS and substorms to infer that quiettime SAPS were almost always associated with substorms and their durations were well bounded by that of the substorms for most cases. Next, we extend this analysis over to a statistical study of quiet-time and disturbed-time SAPS events identified over two years. From this study, we find quiet-time SAPS to occur between the relatively narrow nightside MLT range of [18, 4] whereas disturbed-time SAPS was found to occur between the broader nightside MLT range of [15, 5]. We also find the occurrence percentage of quiet-time SAPS to be at its highest between the narrow latitude range of 60-66⁰, while disturbed-time SAPS was observed to occur within a much broader latitude range of 55-66⁰. Finally, the calibration and validation of a control card used in the SuperDARN radar transmitters, is discussed. / Master of Science

The earth's ionosphere-thermosphere region is a coupled environment which is governed by interactions between the overlapping neutral constituents and ionospheric plasma. The mid-latitude thermosphere-ionosphere system is very complex owing to its sensitivity to both the polar and equatorial processes. The mid-latitudes is also a relatively unexplored and less understood region primarily due to the paucity of observing instruments that have traditionally been available. However, the past 9 years of mid-latitude expansion of the Super Dual Auroral Radar Network (SuperDARN) has provided new access to continuous large-scale observations of the sub-auroral ionosphere. On the other hand, the past 3 years of mid-latitude expansion of the North American Thermosphere Ionosphere Observation Network (NATION) Fabry-Perot interferometer array, has created a critical resource for measuring the thermospheric neutral winds. The overlap of these two observing networks in the mid-east North American sector has resulted in a strong ground-based large-scale platform for co-located study of mid-latitude thermosphere-ionosphere dynamics for the first time. The coupling between ions and neutrals is a very important process for controlling the thermospheric dynamics. Ion-neutral coupling at high latitudes has been studied in many previous papers, but there have been very few studies focused on the mid-latitude region. Hence, in this work we have studied the ion-neutral coupling mechanisms and timescales at mid-latitudes during disturbed geomagnetic conditions by using the co-located observations from the SuperDARN-NATION array. The study has focused on the main phase as well as the late recovery phase of a geomagnetic storm which occurred on October 2-3, 2013. Ion drag is known to drive the neutral circulation during the main phase of storm at auroral latitudes, while the neutral wind disturbance dynamo mechanism is known to generate ionospheric electric fields and currents during the recovery phase. By using the methods of ion-neutral momentum exchange theory and time lagged correlation analysis, we analyzed the timescales at which the ion-neutral coupling operates. The ions are observed to drive the neutral winds on a timescale of ~ 84 minutes in the storm main phase which is significantly faster than expected from the driving due to local ion-drag alone (~ 124 minutes). This suggests that along with ion-drag, other local and non-local storm-time influences like Joule heating are also playing an important part in driving the neutral winds. On the other hand, in the late recovery phase, the neutral winds are found to be strongly coupled with the ions and maintain the ion convection without any significant time delay which is consistent with effect of the 'disturbance dynamo' or 'neutral-flywheel' persisting well into the late recovery phase. The timescales and underlying physics understood through this work serve as an important contribution to our knowledge of ion-neutral coupling processes at the middle latitudes. Looking forward, the expansion of co-located SuperDARN-NATION coverage at mid-latitudes, and developments in the tools of large-scale visualization through FPI wind field mapping and SuperDARN convection maps, has created a very strong basis for using the results and analysis tools developed in this work for large-scale ion-neutral coupling characterization in future. / Master of Science

The data from the new mid-latitude radars of the Super Dual Auroral Radar Network (SuperDARN) provide new types of challenges and observations. We have developed a method for identifying periods of ionospheric backscatter that increase the number of data and reduce the average velocity in agreement with previous incoherent scatter radar (ISR) studies. Analysis of the data identified by this method clearly shows that different types of ionospheric irregularities are being observed in the mid-latitude region. One type of irregularity is clearly subauroral and equatorward of the plasmapause. Fitting a convection pattern to the Doppler velocities associated with subauroral ionospheric scatter reveals some interesting features. Subauroral convection is shown to be westward thought most of the night, with an eastward turning near dawn. The rotation factor of the ionosphere relative to the rotation of the earth is shown to be ~0.95, which is in good agreement with previous studies of plasmaspheric corotation. / Master of Science

One of the intriguing features of the F-region ionosphere are anomalous evening enhancements of the electron density over certain mid-latitude sites. The most prominent example of this enhancement is the Weddell Sea Anomaly. Although the evening anomalies have been known for several decades, their generation mechanisms are still under debate and their accurate modeling remains a challenge. In this dissertation, the role of thermospheric neutral winds in the generation of these anomalies is investigated. Thermospheric winds play an important role in the dynamics of the F-region ionosphere, and, as it will be shown, in the generation of the evening anomalies. However, to date, their reliable estimation remains a challenge. To mitigate this shortcoming, data assimilation models were employed. First, seasonal global maps of F-region peak parameters (NmF2 and hmF2) from COSMIC radio occultation measurements were assimilated into the Global Assimilation of Ionospheric Measurements Full Physics (GAIM-FP) model. The model estimates magnetic meridional winds at low and mid-latitudes. GAIM-FP estimated winds were shown to be in good agreement with independent ground-based wind observations. Next, in order to address the role of neutral wind components in the generation of anomalies, a separate, 3-D physics-based Thermosphere Wind Assimilation Model (TWAM) was developed. TWAM is based on an implicit Kalman filter technique, and combines GAIM-FP magnetic meridional wind data with the equation of motion of the neutral gas to provide the climatology of the thermospheric wind components. The neutral wind components estimated by TWAM were also found to be in close quantitative agreement with independent ground-based wind observations, and were shown to accurately reproduce NmF2 and hmF2 over the anomalies. To understand the physical mechanism behind the anomalies, the plasma production, loss, and transport processes were analyzed. It was found that, due to the action of the equatorward wind, the evening density maximum forms at altitudes where the recombination rate is relatively small. It was revealed that at this time and altitude, plasma loss due to transport also weakens. As a consequence, the relative role of solar production increases over the net loss process and the electron density enhancement occurs.

In this thesis, the role of mid-latitude cyclones in air pollution transport in the Northern Hemisphere is quantified. The storm tracking model, TRACK, is used to study the mechanisms through which pollution, specifically ozone (O3) and carbon monoxide (CO), are vented from the boundary layer to the free troposphere and thus transported over large distances, as well as the introduction of O3 from the stratosphere into the troposphere. The relationship between mid-latitude cyclones and air pollution transport of O3 and CO is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis, a combined meteorology and composition reanalysis dataset. A comparison between springtime surface ozone measurements at rural background sites on the west coast of Europe and cyclone track frequency in the surrounding regions was used to first establish the correlation between cyclone location and surface air quality. The focus is on spring as it tends to be the season of maximum intercontinental transport of O3. The surface observations were compared to the MACC O3 values at the same locations and case studies of how cyclones can influence surface O3 measurements are described. When cyclones track north of 53°N, there is a significant probability that the surface O3 will be high (> the 75th percentile), due to the close proximity to stratospheric intrusions and the transport at low levels across the North Atlantic Ocean. The most intense spring cyclones (95th percentile) were selected for two regions, the North Atlantic and the North Pacific, for further investigation into the mechanisms which impact O3 and CO concentrations near cyclones. These intense cyclones ( 60 over each region) often tracked over the major emission sources of eastern North America and East Asia. The distributions of MACC O3 and CO within a "typical" intense cyclone are examined by compositing the cyclones together. The cyclone-centered composites were compared to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the cyclone locations. Mid-latitude cyclones are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the cyclone. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This work was expanded to identify the links between teleconnection patterns, mainly the North Atlantic Oscillation (NAO), that affect the major storm track pathways in the North Atlantic sector and the distribution of MACC O3 and CO throughout the troposphere and lower stratosphere. For this analysis, TRACK was used to calculate seasonal weighted-average O3 and CO distribution maps based on the monthly NAO index. During positive NAO phase, the persistence of low pressures over the North Atlantic coupled with the Azores High promotes transport across the North Atlantic throughout the troposphere. During negative NAO phase, blocking high pressure in the eastern North Atlantic are known to occur, which shifts transport pathways to a more southerly zonal flow. This work demonstrates the complex relationship between the horizontal and vertical distribution of pollution, including surface concentrations, and synoptic-scale systems.

The equatorial Quasi Biennial Oscillation (QBO) is known to be an important source of inter-annual variability at mid and high latitudes in both hemispheres. Coupling between QBO and the polar vortex has been extensively studied over the past few decades, however, less is known about QBO influences in the mid-latitude mesosphere. One reason for this is the relative lack of instrumentation available to study mesospheric dynamics at mid-latitudes. In this study, we have used the mid-latitude SuperDARN HF radar at Saskatoon (52.16 N, -106.53 E) to study inter-annual variation in mesospheric winds. The specific aim was to determine whether or not a Quasi Biennial signature could be identified in the Saskatoon mesosphere, and if so, to understand its relationship with the equatorial stratospheric QBO. To achieve this goal, a technique has been developed which extracts meteor echoes from SuperDARN near-range gates and then applies least-squares fitting across all radar beam directions to calculate hourly averages of the zonal and meridional components of the mesospheric neutral wind. Subsequent analysis of 13 years (2002-2014) of zonal wind data produced using this technique indicates that there is indeed a significant QBO signature present in Saskatoon mesospheric winds during late winter (Jan-Feb). This mesospheric QBO signature is in opposite phase with the equatorial stratospheric QBO, such that when QBO (at 50 hPa) is in its easterly (westerly) phase, the late winter winds in Saskatoon mesosphere become more (less) westerly. To further examine the source of the signature, we also analyzed winds in the Saskatoon stratosphere between 5 hPa and 70 hPa using the ECMWF ERA-Interim reanalysis data set, and found that the late winter stratospheric winds become less (more) westerly when QBO is easterly (westerly). This QBO signature in the mid-latitude stratospheric winds is essentially the same as that observed for the polar vortex in previous studies but it is opposite in phase to the mid-latitude mesospheric QBO. We therefore conclude that filtering of gravity waves through QBO-modulated stratospheric winds plays a major role in generating the mesospheric QBO signature we have identified in the Saskatoon HF radar data. When the Saskatoon stratospheric winds are anomalously westward during easterly QBO, the gravity waves having westward momentum might be filtered out, depositing a net eastward momentum in the mesosphere as they propagate upwards. This would result in increased westerly mesospheric winds at Saskatoon. The opposite would happen when the equatorial QBO is westerly. / Master of Science

This thesis presents the distribution of strong wind and wind pressure in the Greater Victoria area associated with winter mid-latitude cyclones based on climate data from the School-Based Weather Station Network during 6 selected days in the winters of 2006, 2007 and 2008. The objectives of this study are i) to test whether synoptic conditions favourable to severe mid-latitude cyclonic storms that are well described in the literature were associated with the selected storms, ii) to determine the time patterns of high wind speed and its direction and maximum gusts, iii) to test necessity of considering the spatial variation in air density and its controls in general assessments of the spatial variation in wind pressure and wind damage potential in the local area, iv) to identify potential areas susceptible to wind damage. Observations taken every second were from Davis Vantage Pro2 TM Plus weather stations located on the southern edge of school building roofs. Thirty-minute means and gust wind speeds were used. All six storms went north of Victoria. The synoptic conditions associated with the selected mid-latitude cyclones agreed with the ones described in literature. Strongest winds at most stations were generally from the southwest, and multiple wind speed peaks were found. The daily iii  maximum gust wind speeds were found before and/or after the highest mean wind speed peak. The spatial variation in air density and its controls were found to be negligible. Although there are a number of interacting causes of the distribution, strongest winds were at stations with smooth surrounding surfaces, close to the southern shoreline, on exposed slopes and/or near relief constrictions. The area with greatest wind speeds and damage potential was found from the east of downtown extending to Lansdowne Middle School. This study provides new knowledge of winds in the Greater Victoria area and contributes to people’s better response to wind storms, land use planning and forecasting severe windstorms. / Graduate / 0368 / mmatsuda@uvic.ca

This thesis presents the distribution of strong wind and wind pressure in the Greater Victoria area associated with winter mid-latitude cyclones based on climate data from the School-Based Weather Station Network during 6 selected days in the winters of 2006, 2007 and 2008. The objectives of this study are i) to test whether synoptic conditions favourable to severe mid-latitude cyclonic storms that are well described in the literature were associated with the selected storms, ii) to determine the time patterns of high wind speed and its direction and maximum gusts, iii) to test necessity of considering the spatial variation in air density and its controls in general assessments of the spatial variation in wind pressure and wind damage potential in the local area, iv) to identify potential areas susceptible to wind damage. Observations taken every second were from Davis Vantage Pro2 TM Plus weather stations located on the southern edge of school building roofs. Thirty-minute means and gust wind speeds were used. All six storms went north of Victoria. The synoptic conditions associated with the selected mid-latitude cyclones agreed with the ones described in literature. Strongest winds at most stations were generally from the southwest, and multiple wind speed peaks were found. The daily iii  maximum gust wind speeds were found before and/or after the highest mean wind speed peak. The spatial variation in air density and its controls were found to be negligible. Although there are a number of interacting causes of the distribution, strongest winds were at stations with smooth surrounding surfaces, close to the southern shoreline, on exposed slopes and/or near relief constrictions. The area with greatest wind speeds and damage potential was found from the east of downtown extending to Lansdowne Middle School. This study provides new knowledge of winds in the Greater Victoria area and contributes to people’s better response to wind storms, land use planning and forecasting severe windstorms. / Graduate / 0368 / mmatsuda@uvic.ca